Aberrant cell cycle regulation in CAF-1 knockout mutants of Arabidopsis and homologous recombination

Abstract

Chromatin assembly factor-1 (CAF-1) deposits histones onto DNA templates after replication and DNA repair synthesis. In Arabidopsis, the FAS1, FAS2 genes encode CAF-1 subunits, p150, p60. To determine the influence of CAF-1 on genome stability in plant, we have analyzed FAS1 and FAS2 mutants on homologous recombination (HR) repair. These mutants show higher sensitivity to gamma-ray irradiation. Expressions of the AtRAD51 and AtRAD54 genes that play a central role in HR are increased. The recombination assay revealed frequencies of HR were 40-fold increased in the FAS1 and FAS2 mutants. Furthermore enhanced T-DNA integration was observed in both mutants. These data suggest that, the defective CAF-1 function per se increases double strand DNA breaks (DSBs) at the S phase of cell cycle and enhance HR. Retarded chromatin assembly due to defective CAF-1 function also enhances T-DNA access and probably recruitment of HR machinery at the site of DSBs.